<i18n dev> RFR: 8361519: Obsolete Unicode Scalar Value link in Character class

[Naoto Sato]

Refining the description of "Unicode Scalar Value" in the `Character` class.
The original description referenced the outdated Unicode 3.1 specification, which previously included the U+xxxx notation but no longer does. Updated the reference to point to the Unicode glossary, which defines the term more accurately. Additionally, replaced the obsolete `@spec` link to Unicode 3.1.0 with a reference to the current Unicode Character Database.

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Commit messages:
 - initial commit

Changes: https://git.openjdk.org/jdk/pull/26169/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26169&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361519
  Stats: 6 lines in 1 file changed: 0 ins; 2 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/26169.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26169/head:pull/26169

PR: https://git.openjdk.org/jdk/pull/26169